DE1110455B - Device for determining the position of a document with regard to a label on it - Google Patents

Description

The invention relates to a method for determining the position of a document with respect to of a license plate located on it. This task occurs z. B. letters, bank checks, banknotes and the like, which are to be sorted with respect to their destination or recipient or the like. A There is a particular need for this when sorting such documents in the postal service. The description the invention is therefore primarily directed to a method for recognizing the position of mail items, without the invention being restricted thereto.

In order to be able to carry out a sorting, it is necessary that the documents (letters, cards and the like) are guided past the sorter with correct reading. But since they are on the conveyor belt on the they are guided past the sorter, can occupy different layers, it is necessary to turn over the illegible documents. The number of possible layers is limited to four, if it is assumed that a special device takes care of the longer edges of the documents Always lie horizontally in the conveyor system, so that 90 "rotations are excluded are.

Can be used as a characteristic mark for letters to look at the stamps. One can also assume that, in the case of letters that are correctly readable, the stamps are in the upper right corner. In order to determine the position of the letters, it is therefore necessary examine the upper right corner of the letter. The result of the investigation is then for the control of a subsequent operation in which the letters are sorted according to their position are used.

It is possible to examine marks on documents by various methods make photoelectric scanning. One possibility would be e.g. B. in it, the documents a conveyor system, e.g. B. an edgewise conveyor belt to continuously pass the scanning device and to move the scanning beam back and forth perpendicular to the direction of movement. As soon as that Characteristics hit by the scanning beam are intensity fluctuations in a photocell caused, which is then used via amplifier to generate a corresponding control pulse could become. Depending on whether the intensity fluctuations in the upper or lower Half of the letter occur, the generated impulse is used for sorting with subsequent rotation or for Used to sort without rotating the letter. At the facility to determine the location

of a document regarding one on him

located license plate

Applicant:

Standard electrical system Lorenz Aktiengesellschaft, Stuttgart-Zuffenhausen,
Hellmuth-Hirth-Str. 42

Dr.-Ing. Karl Steinbuch, Fellbach (Württ.),
has been named as the inventor

a known device, the letters are guided past a fixed photocell and the Output signals fed to a relay via a transformer, which in turn initiates a switching process for Sorting the letter controls.

With such investigation methods, however, errors can easily occur, since there are on the documents still other characters, e.g. B. address or sender notes and the like., Can be found under Cause a fluctuation in intensity similar to that of the license plate. Although one has the last-mentioned known device switched off the detection of characters in that you use a color-selective photocell, but you are then on a color of the stamps, z. Bread, limited.

The invention is based on the object of avoiding or reducing such incorrect evaluations Photocell selectivity to be unlimited. The invention relates to a device for Determining the position of a document with regard to a label located on it, in particular of a letter with regard to its postage stamp, by means of photoelectric scanning, in which the document continuously passed a photocell and the signal value resulting from the scanning with a fixed, predetermined threshold value, which, when exceeded, results in the identification of the identifier characterizing process is triggered, is compared.

According to the invention, essentially only one characteristic is used as the variable comparison value corresponding DC component of the signal

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used, which is determined by the fact that the incoming photocell signals simultaneously one High-pass filter and a low-pass filter with parallel outputs and the output signals of the The high-pass is reversed and rectified after passing through a second low-pass to the off the signals emerging from the first low-pass filter are added.

This measure is advantageous so that, if necessary, the scanning can be carried out with an areal or a slit photocell. The latter type of photocell is required if you are narrow Areas, e.g. B. wants to evaluate the white stamp edges on dark letters. With the arrangement According to the invention, it is now possible to examine an entire area of characteristics in any case. At the same time, however, one also achieves with the new device that with a gap-like scanning all Brightness transitions caused by other recordings, e.g. B. by the Scriptures are conditioned, not with are detected, while a unique identification signal is retained, which is associated with a corresponding Threshold value can be compared well.

The invention is explained in more detail using an example. It shows

1 shows a photocell signal produced when scanning a letter suitable for reading,

Fig. 2 is a schematic representation of the device of the invention,

FIGS. 3 a to 3 c are diagrams of the individual parts of the device according to FIG Signals.

The letters are continuously conveyed past the scanning device on an upright conveyor belt, whereby the photocell signal shown in Fig. 1 is produced. The intensity peaks before the broad one Signals that correspond to the postage stamp are caused by the writing or other characters on the letter. In all diagrams it is assumed that the zero line corresponds to the white value and with increasing Ordinate value the signal approaches the black level.

The postage stamp signal contains α, as can be seen from FIG is, a large proportion of direct current, while this proportion is lower in the other parts of the letter is. This difference can therefore be used to identify the location of the postage. The easiest way is to specify a value between the two expected direct current values, so that, as is known, if this value is exceeded, a postage stamp is inferred can.

The greater the difference in the direct current components, the better the threshold value can be determined is. It is therefore ensured that the signals produced by writing or the like are as possible are suppressed, whereby the direct current component of these letter areas is significantly lower, in particular Cases becomes zero.

Fig. 2 shows a device for forming the peak value while switching off the signals caused by scripture. The photocell signal resulting from scanning by a photocell 1 becomes after amplification in an amplifier 2 at the same time a low-pass filter 3 and a High pass 4 supplied. The low pass 3 smoothes the curve, so that the signals caused by the writing are largely suppressed. The output signal of the Low pass 3 is shown in Fig. 3a. In itself, this signal could be used to to be compared to a threshold, yet the difference between the postage stamp and the in the rest of the area and can almost completely disappear in unfavorable cases. The scanning signal is therefore at the same time fed to the high-pass filter 4, at the output of which the higher-frequency signals occur, as shown in Fig. 3b .. These signals are rectified by a rectifier, so that only the negative part of the signals is allowed through. The rectified signals are then fed to a low-pass filter 6, which is similar to the low-pass filter 3 and smooths the curve. The output signals of the low-pass filter 6 are shown in Fig. 3c. The output signals of the two low-pass filters 3 and 6 are now added in an adder 7. As can be seen from FIGS. 3 a and 3 c, compensate each other in addition, the signals caused by the writing wholly or almost entirely. It stays that way for him Postage stamp location left a distinct broad signal, whose DC value well against a threshold value can be delimited.

The differential signal is fed to a comparison device 8, in which it is compared with the threshold value is compared. If the threshold value is found to be exceeded, the recognition can be made a postage stamp to be closed. A control signal is issued when the threshold value is exceeded generated, which is used to trigger appropriate control operations for the scanned letter.

Claims (1)

PATENT CLAIM: Device for determining the position of a document with regard to a label located on it, in particular a letter with regard to its postage stamp, by means of photoelectric scanning, in which the document is continuously moved past a photocell and the signal value resulting from the scanning with a fixed predetermined threshold value at the exceeding of which a process characterizing the identification of the identification is triggered, is compared, characterized in that essentially only the direct current component of the signal corresponding to a identification is used as the variable comparison value, which is determined by the fact that the incoming photocell signals simultaneously a high-pass filter (4 ) and a low-pass filter (3) with outputs connected in parallel and the output signals of the high-pass filter (4) are reversely rectified and, after passing through a low-pass filter (6), are added to the signals emerging from the low-pass filter (3) will. Considered publications:
U.S. Patent Nos. 1729,521, 2,507743. 1 sheet of drawings © 109 620/222 6.61